A side view of the Peacock Mantis Shrimp.  Courtesy of Roy L. Caldwell


Secret Weapons Exposed

      The peacock mantis shrimp is a very beautiful looking, interesting individual with many complex features that make it unique from other organisms. Just to mention a few things, they have very complex eyes that can see ultraviolet light, and a very powerful defense mechanism adapted for their environment.
       The peacock mantis shrimp is a beautiful creature to say the least. It has a vast array of colors throughout its body. Two peacock mantis shrimp wrestling in the sand.  Copyright of Roy L. CaldwellTheir main part of the body or base, is a green/olive color. Its antennae is made up of brightly colored orange scales, and it has appendages that are a beautiful red color. They also have a pattern similar to a leopard that covers their lower carapace. The eyes have a blue color to them as well (Chui 2013). The reason why they are so colorful is for mating purposes. The colors on the body are transmitted in wavelengths that can be detected by the mantis shrimp. They also use their florescent colors to send visual warning signals to the predators in their habitat (Mesa 2013).
       The average mantis shrimp measures anywhere between about 3-18 cm but have been known to measure up to 38 cm in some rare cases (Chui 2013, Mesa 2013).  The mantis shrimp have a carapace that covers the lower half of the head that leaves a small area open for the eyes. They also have raptorial appendages, a single pair of maxillopods, as well as three sets of legs for walking, and 5 pairs of legs. These legs help the peacock mantis shrimp with moving around, swimming, and help them with excavating their dens (Chui 2013).
       One of the few features that makes the Peacock mantis shrimp very unique is its very advanced pair of eyes it has adapted for life on the coral reef. They are known to have some of the most advanced eyes in the animal kingdom, having around 12-16 different photoreceptors types in their eyes. These sample a small set of perceivable wavelengths ranging anywhere from very ultraviolet rays to far red colors. Most animals only use around 3 or 4 to accurately discriminate colors. The reason why stomatopods, like the peacock mantis shrimp use 12 photoreceptors is because it would “allow for extremely rapid color recognition without the need to discriminate between wavelengths within a spectrum” (Hanne et al. 2014, Rose 2009). They need these special eyes because the live in shallow coral reefs, one of the most colorful environments in the world, and scientists believe that their complexly colored bodies are involved in a complex communication system. They use their bodies and vibrant colors to communicate with predators to warn them. The females also use their bodies to communicate with the males to tell them when the best time to mate is by reading the moon for tidal cycles (Mesa 2013). By reading the tidal cycles, they can figure out when the best times to mate are so then the males don't waste their efforts.  They also use this special vision to help the make quick, accurate color signal judgments under conditions with changing light about predators, prey, and just other information about their surroundings that aid in survival (Hanne et al. 2014).

Peacock Mantis Shrimp Close Up on Eyes. Copyright National Aquarium

      Another interesting structure that the peacock mantis shrimp possesses is its club like defense mechanism. They have a raptorial appendages that are in the shape of a small club. These small clubs can reach speeds of 23 meters per second and can accelerate around 10,400 g. Scientists have recorded impact forces ranging from 400-1500 N. Due to such fast movement, the cause cavitation bubbles to form which bombard their enemies/prey with and additional force of up to 504 N (Rose 2009). The cavitation bubbles can produce light and heat that can reach up to several thousand Kelvin and produce a intense snapping sound. With such force the Peacock mantis sharp can crush shells of prey and have been known to break tanks in aquariums.
     How does this mechanism work? Well there are structures that are called sclerites that when engaged, keep the club/hammer appendage in place.Side view of the peacock mantis shrimp.  Copyright of Roy L. Caldwell The contain a saddle like structure located near the top of the appendage that is really flexible and is important in the reduction of the bucking during the striking motion, and adds 10% of stored energy to the limb. The majority of the other energy is stored in a structure called the “meral-V” which is next to the saddle which functions as the spring where energy is stored without causing harm the mantis shrimp. Then when it wants to attack it disengages the latches and all the other structures collectively, and all the built up energy is released causing a large amount of force to be generated to attack either prey, or predators (Rose 2009). The pair of raptorial appendages they have help keep predators near the coral reefs in check and aid them in fighting and feeding on prey such as snails, clams, and crabs such as the red rock crab (C. productus).

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